UNIVERSITY OF CALIFORNIA
COLLEGE OF AGRICULTURE
AGRICULTURAL EXPERIMENT STATION
CIRCULAR No. 285
SWEET POTATO PRODUCTION
J. T. EOSA
The sweet potato is one of the leading truck crops of the United
States, but at the present time it is only of minor importance in Cali-
fornia. In 1922, the year of heaviest production, there was grown in
the United States 1,117,000 acres of sweet potatoes, producing
109,394,000 bushels. The crop provided approximately 55 pounds of
sweet potatoes per capita for the entire population of the United
States. In the same year the acreage of sweet potatoes in the states
west of the Rocky Mountains was : California 8000, Arizona 2000 and
New Mexico 1000, a total of 11,000 acres, producing 1,292,000 bushels.
Therefore, for the seven and one-half million people living in the eight
states west of the Rockies, there was produced in this district only
about 10 pounds of sweet potatoes per capita. This small production
in the western states as compared with that of the country as a whole
has resulted in a low per capita consumption of sweet potatoes and
their shipment from the southern and middle western states to the
Pacific coast markets. Thus, in 1923, Los Angeles received 41 cars of
sweet potatoes from Californian points, 35 cars from Arkansas, and 9
cars from other states. The sweet potatoes supplied to western markets
are often rather poor in quality and inadequate for the market
demands. The retail price, moreover? is too high to encourage large
consumption, except during that brief portion of the year when the
crop is being harvested and most growers are hurrying their product
On the other hand, returns to the grower have not always been
satisfactory because much of the crop is sold during the temporary
Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
over-supply of the markets at digging time in the fall. The 1922 crop
was an example of such a condition. Prices during the fall were so
low that the crop of some fields was not dug at all — yet by the following
February the wholesale price had risen to 5 cents a pound for the
properly cured storage house product. Adequate storage facilities
would make it possible to market at more satisfactory prices many
more sweet potatoes than are now grown in California. Adequate
storage facilities would tend to eliminate such uneconomical practices
as shipping sweet potatoes from Arkansas, Tennessee, and other dis-
tant regions, to Pacific coast markets. The usual seasonal variation in
prices of sweet potatoes is indicated by figures 1 and 2.
Fig. 1. — Seasonal range in jobbing prices on Jersey and Nancy Hall sweet
potatoes at San Francisco, 1922-1923.
Factors that must be considered if yields, production, demand and
consumption of sweet potatoes are to.be increased, are disease control,
and the production of varieties or types that are more popular with
the consumer. Two diseases commonly known as stem rot and black
rot in many cases are destroying 10 to 50 per cent of the crop. Both
are controllable to a large extent by well proven methods. Varieties
of the sweet, moist-fleshed type, such as Nancy Hall and Porto Rico
Yam, are not only more productive and better for storage than the
dry meally Jersey type now so generally grown, but are preferred by
SWEET POTATO PRODUCTION IN CALIFORNIA
It is the purpose of this circular to give such information regarding
sweet potatoes as is available and applicable to California conditions,
and as is thought necessary to increase the yield and the market
, — 1
Fig. 2. — Seasonal range, jobbing prices on sweet potatoes,
San Francisco, 1923-1924.
REQUIREMENTS FOE GEOWING SWEET POTATOES
Soils. — Areas for commercial sweet potato production are limited
by the special soil requirements for growing this crop, especially under
irrigated conditions. Generally, light sandy loam and coarse sandy
soils are most suitable. Fresno Sand and Oakley Sand are the soil
types most used for sweet potatoes. The fertility necessary as com-
pared with that required by other crops is not very high. Yet some
of the sandy soils on which sweet potatoes are now grown, would
probably produce larger crops if organic matter and commercial
fertilizers were added. The physical texture of the soil seems to
4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
affect both the form, size, and smoothness of the potatoes. On the
heavier soils, the top growth is likely to be so excessive as to retard
maturity and cause inconvenience in digging. One advantage of sandy
soils is that they retain less of the irrigating water than do heavy
soils. The plants grown on sandy soils, therefore, suffer less from
excessive moisture. There is a considerable range in the soil adapta-
tion of different varieties. The Jersey type, especially, requires sandy
soils, while the Nancy Hall, Porto Rico, and some of the large white
varieties will develop satisfactorily on medium-heavy loam soils.
Climate. — The sweet potato requires a long warm growing season.
The plants are very sensitive to frost and therefore cannot be set in
the open field until danger of frost is over. Since the tops are also
killed by the first heavy frost in the fall, the crop should be dug before
or soon after the first frost. The normal development of the plant is
retarded by cool cloudy weather during the growing season, and regions
having cold nights during the summer are not favorable. Hence,
sweet potatoes are grown in California only at some distance from
the coast, except south of Los Angeles.
Moisture. — While the sweet potato plant probably uses as much
water as any other crop having the same amount of foliage and grown
under the same conditions, the fact remains that the plant is not
injured seriously by rather long periods of drought. This has led to
the idea that sweet potatoes are a drought-resistant crop. Excellent
crops have been grown in the Turlock district, on sandy land, without
irrigation, but such soils are usually sub-irrigated to some extent from
nearby canals. Good growth and yields have been observed where
by mid-summer there was no available soil moisture nearer than 20
inches to 2 feet from the surface. On higher lands which are not sub-
irrigated, regular surface irrigation by the furrow method is practiced.
SWEET POTATO DISTEICTS
The larger portion of the sweet potato acreage of California is
located in Merced and Stanislaus counties in the extensive area of
sandy soils adjoining the main line of the Southern Pacific railway.
Both soil and climate are very favorable for maximum yields of sweet
potatoes of good quality. Smaller sweet potato districts are located
in Los Angeles County, in the San Fernando and San Gabriel valleys,
and in Orange and San Diego counties. Sweet potatoes have also
been grown successfully in the upper part of the Sacramento Valley,
at Redding ; in Kern County, at Bakersfield and Shafter ; in southwest
Fresno County, and to a small extent in the Imperial Valley near
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA
GEOWING THE PLANTS
Sweet potatoes are usually propagated by means of plants produced
from small potatoes placed in a hotbed, with proper moisture and
temperature conditions. The sweet potato itself consists of a root,
originally a fibrous feeding root, which in process of development has
thickened for a greater or less distance from the central stem. On
each such thickened root, or potato, are found four rows of lateral
fibrous feeding roots, which usually disappear before the crop matures,
so that only the slight depressions where these roots were attached can
be seen. From the neighborhood of these root scars, adventitious buds
originate, and under favorable growing conditions, sprouts are formed.
These sprouts have an independent root system and are only weakly
connected with the mother potato, from which, however, they derive
most of their food up to transplanting time. The sweet potato root
has no true rest period, for the sprouts may start growing at any time
moisture and temperature conditions are suitable. This often occurs
in the storage house in the early part of the storage season, also
in the field before harvest, when the partly developed roots are
separated from the main stem by diseases.
The potatoes used for propagating are called "seed" or "seed
stock." The smaller potatoes ranging from one to two inches in
diameter are most suitable for this purpose. Larger potatoes may
be used, but they are more expensive and do not produce so many
plants from a given quantity of seed stock. Where it is necessary
to use large potatoes, the yield of plants can be increased by splitting
the potatoes lengthwise, and bedding with the flat side down. The
selection of sweet potato seed is discussed in detail at the end of this
circular. Growers in the Turlock district allow about 400 pounds
of seed for each acre to be planted. From 10,000 to 14,000 plants to
the acre are required, depending on the distance of planting. If there
is no disease, the seed disinfected, the hotbed properly prepared and
carefully handled, 200 pounds of seed should produce enough plants
for one acre.
Preparation of the Hotbed. — The bed for growing sweet potato
plants is usually heated with fresh stable manure. It should be located
in a warm, sunny, well-drained spot, and protected from north winds,
by a fence or windbreak. A trench is dug 6 to 8 feet wide and 15
inches deep, and as long as necessary to accommodate the quantity of
seed to be bedded. When plants for a large acreage are grown, it is
best to arrange the plant beds in short sections parallel to each other.
Several days before the sweet potatoes are bedded, the trench should
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
be filled with fresh heating horse manure which is first packed by
tramping", then covered with a layer of 3 to 4 inches of sandy soil or
sand. On this the seed potatoes are laid about one-half inch apart,
when the bed has become warm. The seed should be covered at once
to a depth of three inches. The best material for covering is clean
sand, preferably taken from a creek bed or sand pit where con-
tamination by sweet potato diseases is unlikely. As the plants or
"sprouts" can obtain all the necessary nutriment for their develop-
ment from the mother seed potato, there is no need for a fertile soil
Cp 5C> O G> p?OQQf
•«/- S<J ; • -«- c ~
Fig. 3. — Fire-heated hotbed. Above is shown cross-section of the bed. The
flue-space extends the entire width and length of the bed and is covered with
rough flooring. Over this is a layer of tamped soil or clay from 3 to 6 inches
deep, above which is the sand in which the potatoes are bedded.
Below is shown a side-section, showing arrangement of furnace and flue.
in the plant bed. Furthermore, sand does not bake and crust in such
a way as to prevent the sprouts emerging, as heavier soils often do.
Also the formation of fibrous roots on the plants is much more extensive
when grown in sand, than in heavier soils. The last is an important
factor, especially with varieties such as the Nancy Hall, which form
fibrous roots sparingly and are therefore more difficult to transplant
successfully. Plants grown in sand are also pulled up more easily
and with less damage to the root system. Another advantage of using
SWEET POTATO PRODUCTION IN CALIFORNIA
clean sand in the preparation of the sweet potato plant bed is the
avoidance of diseases, especially black rot and stem rot, which are
likely to be harbored in soils taken from the cultivated fields, or which
have been used for sweet potato beds in previous years.
Other Types of Hotbeds. — Because of the increasing difficulty of
obtaining sufficient quantities of fresh stable manure for the prepara-
tion of large plant beds each year, other methods of heating the beds
may have to be resorted to. The flue-heated bed, one type of which
is shown in fig. 3, is well suited for growing sweet potato plants. A pit
Fig. 4. — Top view of fire-heated hotbed, concrete construction. (Courtesy
New Jersey Experiment Station.)
is located at one end of the bed. Recessed beneath the bed, and open-
ing into this pit, is a brick furnace, which may be equipped with a
grate for burning coal or briquettes. The smoke, fumes, and heat
from the firebox are conducted beneath the plant bed, either through
tile flues spaced 3 feet apart and entering a chimney at the far end
through a header ; or the hotbed may have a tight floor, with an open
space beneath, extending for its entire width and length and connected
with a chimney at the far end. Heaters of either of the above types
may accommodate beds 8 to 12 feet wide and 40 feet long. For larger
beds, it may be more economical to use coils of pipe for steam or hot
8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
In the cooler sections, sweet potato beds are enclosed by a frame
of 1 by 12 inch boards and covered with glazed sash or medium weight
unbleached muslin cloth, water-proofed by treatment with hot raw
linseed oil. In the warmer sections, including the Turlock district
and the lower San Joaquin Valley, the beds are seldom enclosed, but
are covered with board shutters 3 to 4 feet wide and slightly longer
than the bed is wide. These shutters are placed on the surface of the
beds at bedding time, to retain the heat in the bed. m After the bed has
once warmed up, there is danger of over-heating, and the shutters are
removed from time to time to regulate the temperature. When the
plants begin to push through, the shutters are permanently removed.
A thermometer should be placed near the center of the hotbed, and the
temperature kept around 80° F. until the sprouts have started.
One of the most important steps in the control of sweet potato
diseases is disinfection of the seed potatoes before bedding. This is
especially important in the control of black rot, both in the hotbed
and after transplanting to the field. It is also helpful in controlling
other diseases. It should be remembered that seed treatment is only
one step in the control of sweet potato diseases, and will not be very
effective unless the other precautions for disease prevention — seed
selection, clean hotbed soils, and rotation of crops — are also observed.
Seed treatment is intended to destroy the disease organisms on the
surface of apparently sound healthy seed. Under the influence of the
warmth and moisture of the hotbed these organisms grow and attack
the young sprouts. Many of the plants are often killed in this way
in the hotbed before transplanting, and many others are infected
and die later in the field, reducing the stand, and lessening the yield.
The standard method of disinfecting seed sweet potatoes is by
dipping the seed for 10 minutes in a solution made up at the rate of
one ounce of corrosive sublimate (Bichloride of mercury or Mercuric
chloride) to 8 gallons of water. The corrosive sublimate should be
dissolved beforehand in a gallon of hot water, to which may be added
one pound of common table or bulk salt to hasten the process. Fairly
rapid solution can be obtained even in cold water with this mixture
of the corrosive sublimate and table salt.
It is usually convenient to dip lots of from 60 to 75 pounds of seed
at a time, using a 50- or 60-gallon wooden barrel containing 32 gallons
of the solution. Dipping the seed for longer than 10 minutes is likely
to cause injury.
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA 9
As the corrosive sublimate reacts quickly with any sort of metal,
the solution should be prepared and handled only in wooden, stoneware,
glass or enameled containers. As it is also deadly poison to all animal
life the powder and the solution must be kept out of reach of children
The solution of corrosive sublimate is weakened by dipping the
seed potatoes. Gunny sacks should not be used for containers in dip-
ping the seed because the jute fibre from which they are made absorbs
large amounts of the chemical from the solution. Wooden baskets or
cotton sacks may .be used, or the seed may be dumped into the solution
loose. The last is the best practice if the barrel or dipping vat is
located on an elevated platform, and is provided with a large drain
plug so that the solution can be promptly drained off into another
barrel at the end of each treatment.
To keep the solution up to the original strength, a small amount of
corrosive sublimate should be added occasionally. It has been found
by experiments that the addition of one-half ounce for every 100
pounds of seed treated, together with enough water to restore the
original volume, will keep the strength of the solution about constant.
If the solution is used over four times without addition of more cor-
rosive sublimate it becomes so weak that the treatment is not effective.
If a stock solution of 4 ounces to the gallon has been prepared, one pint
of this should be added for every 100 pounds of seed dipped.
The seed potatoes, upon removal from the solution, should be
allowed to drain a minute or two, then placed directly in the hotbed,
The transplanting of the plants from the hotbed to the field should
begin as soon as danger of frost is over, and the preparation of the
hotbed should consequently be timed so that the first crop of plants is
ready for transplanting about the time the weather becomes warm
enough for field setting. In the Los Angeles district, transplanting
usually begins about April 1 and continues until the first part of June.
In the San Joaquin Valley, transplanting begins the latter part of
April and continues until late in June. Objections to late planting
are that it is difficult to secure a good stand because of the heat, and
that the shorter growing season reduces the yield. It is the general
experience of growers in California that the earlier transplantings
produce the larger crop. Some experiments in Kern County, con-
ducted by W. B. Camp in 1923, strikingly demonstrate the decrease
in yield from late plantings. The test included Southern Queen, Nancy
10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
Hall, Dooley, Porto Kico, and Big Stem Jersey, the results with all
being similar to those given below for the Jersey variety.
Date Transplanted Besults — Dug October 21
May 21 Good yield. Large uniform potatoes, nearly all marketable.
June 9 Fair yield, many medium size potatoes, 30 per cent small.
June 25 Light yield, nearly all small potatoes.
July 11 Light yield, all small potatoes.
In pulling the plants for transplanting, the mother or "seed
potato" is held in place with one hand and the plants are pulled up
with the other. Plants more than 10 inches high should be pruned
by cutting off the tops of the bundles of plants with a large knife.
After pulling, the plants should be kept out of the sun until trans-
planted. The roots especially should be kept from drying out. Sweet
potato plants may be held for several days after pulling or may be
shipped long distances, if the roots are kept slightly moist, by wrapping
in moistened newspaper. The tops must be kept dry, otherwise slimy
decay takes place within a day or two.
Most of the commercial acreage of sweet potatoes is set with horse-
drawn transplanting machines, of which there are several types on the
market. These machines are equipped with a tank and an automatic
device which discharges a small amount of water at the roots of each
plant as it is set. Even though the soil seems moist at transplanting
time, it is best to use the watering attachment. On very sandy soils,
which dry out quickly, and when transplanting late in spring, it is best
to give a row irrigation within a day or two to moisten the ridges and
give the young plants a favorable start before they have become dry.
Propagation by Vine Cuttings. — In the southern states it is custom-
ary to grow a late crop from vine cuttings or "slips" taken from the
tops of the early crop, which is always grown from plants propagated
in hotbeds. The cuttings of the sweet potato take root readily when
severed from the parent plant and transplanted to a new location
under favorable conditions. Koots form very quickly from the nodes.
The cuttings may be from 10 to 30 inches long, but the shorter
cuttings are much more conveniently handled when transplanted by
machine. Propagation by cuttings does not seem to be generally
advisable in California because of the difficulty of getting a stand in
mid-summer, and the small yield produced by late plantings. Propa-
gating in this way, however, may be desirable for one reason : namely,
the production of potatoes free from disease especially for seed pur-
poses. One of the worst diseases, stem rot, is spread from year to year
within the seed potatoes. The disease works within the stem of the
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA 11
plant, from the root upward. However, cuttings taken from the tips
of vines that appear to be healthy, early in the season, are very likely
to be free of disease, and if transplanted to a field where the soil is also
free from sweet potato diseases will produce healthy potatoes. This
method then results in production of seed that is nearly disease-free,
and may be expected to produce healthy plants if bedded under proper
conditions the next spring. "Slip seed" grown on nematode-free soil
is also the only way to make certain of nematode-free seed.
This practice is known in the South as "slip seeding" and is of
importance in controlling disease, if other precautions are also
observed. A very satisfactory crop of seed was grown at Delhi.
California, in 1924, by this method.
The exact details of culture for sweet potatoes vary in different
localities. A few general suggestions, however, may be useful to the
prospective grower who has had no experience with this crop.
Sweet potatoes are nearly always planted on ridges from 8 to 15
inches high, the lower ridges being generally preferred. Kidge-culture
provides more favorable conditions for the development of the roots,
facilitates row irrigation and reduces the labor of harvesting as com-
pared to flat culture. The rows are generally marked off 3 feet apart,
and the ridges formed with a lister. The riding disc cultivator can
also be used to form ridges after removing all but the two inner discs
and setting these at the proper angle to form a ridge between them.
The tops of the ridges are smoothed slightly with a plank drag before
setting plants, if a transplanting machine is used.
The spacing of plants in the row should be varied to suit conditions.
Varieties that tend to make excessively large potatoes, especially the
Nancy Hall, should be set much closer than varieties that tend to pro-
duce a larger number of medium-sized potatoes, such as the various
strains of the Jersey type. On the more fertile soils all varieties should
be spaced closer than on poorer soils. The average distance between
plants in the row is 15 inches. This may be shortened to 10 inches, or
lengthened to 18 inches, according to the variety and soil fertility.
When the young plants begin to send out runners, it is necessary
to turn these so that they will grow along the ridge and not interfere
with cultivation between the rows. This vine turning is usually per-
formed by hand, but some of the growers equip their cultivators with
rods to lift the vines out of the way. If the tips of the vines are
covered with soil during cultivation they are likely to take root and
12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
form small potatoes which detract from the development of the potatoes
in the main hill. Eventually the vines cover the space between the
rows and cultivation is discontinued, though irrigation may be
continued as late as September 1 on late plantings.
Most of the sweet potatoes in California have hitherto been grown
on sub-irrigated land in the Stanislaus-Merced district with the water
table 4 to 5 feet below the surface during the growing season. With the
lining of the canals to prevent seepage and the pumping being carried
on in some districts to lower the water table, it will probably become
necessary to resort to surface irrigation. The crop can be grown very
successfully with surface irrigation (by the furrow method) but the
cost is greater than under sub-irrigated conditions. Where sweet
potatoes are to be surface-irrigated, the land should be carefully graded
and the water handled so as to get as even a distribution as possible.
During the dry season of 1924 many fields received emergency irriga-
tions and it was found that in those portions of the fields where too
much water was received the potatoes were over-sized and rough, and
many of them cracked.
Even more important is the relation of soil moisture to disease.
During 1924, the portions of the fields that were rather dry or that
received only a moderate amount of water were fairly free from the
black rot disease. In the lower and excessively moist portions of the
fields a very large proportion of the potatoes were affected with black
rot. Careful and uniform distributions of water will do much to
lessen the losses caused by this disease.
On sub-irrigated land two surface irrigations are usually given
shortly after transplanting. On the higher lands, about seven irriga-
tions during the growing season are required.
The time of harvesting depends on market conditions and the
maturity of the crop. Sweet potatoes planted out in May will con-
tinue growing until the tops are frosted in November. The rate of
growth of the potatoes themselves has not been determined for Cali-
fornia conditions, but the increase in yield for the last few weeks of
growth is probably not very great at least for early planted potatoes.
On the other hand, there is a period in the middle of the season when
the increase in size of the potatoes is very rapid.
Harvesting begins in August in central California, and slightly
earlier in southern California. The first sweet potatoes from Imperial
Valley, reach market about July 15. Even the earliest plantings are
SWEET POTATO PRODUCTION IN CALIFORNIA
not nearly full grown when harvesting begins, but the high price
received for the earliest potatoes compensates for the smaller yield.
Harvesting increases in volume through September and October. Prac-
tically all of the sweet potatoes dug before the middle of October are
sold on local markets or shipped at once. Those intended for storage
are harvested from the middle of October until after the tops have
been frosted. The effect of the freezing of the tops on the quality of
the roots is a much disputed question, though it is generally believed
that unless the tops are cut off the day after the first killing frost the
Fig. 5. — Vine cutter, drawn by one horse, used in stripping sweet potato
vines in Virginia. (Courtesy Virignia Truck Experiment Station.)
potatoes will not keep well in storage. Certainly the effect of tem-
perature low enough to freeze the tips of the potatoes themselves, either
before or after digging, is disastrous.
In harvesting, the first step is to dispose of the tops. Most of the
California growers now do this by hand, using long curved knives to
cut them from the central stem. They are then removed and piled in
convenient places to be used later in covering the heaps of potatoes.
Recently the value of the tops as stock feed has been realized, and
many of them are taken from the fields by the dairymen for feeding to
their cattle. The tops may also be clipped from the main stem with a
hoe, and left between the rows so that they will be buried in plowing
out the potatoes. In some eastern districts the slow laborious task of
cutting the tops by hand is avoided by the use of a horse-drawn "vine
cutter, ' ' such as that shown in fig. 5.
14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
After the tops are cut and removed from the ridges, the roots are
plowed out. A 14-inch mold-board plow may be used for this purpose.
Most growers, however, have plows with specially adapted mold-boards
for this work. One grower, Mr. J. B. Steele of Baldwin Park, Cali-
fornia, has adapted an old Irish potato digger for harvesting sweet
potatoes, by removing the elevator apron and welding on an extra wide
and heavy point. The ordinary potato digger has not proved success-
ful with sweet potatoes because of the large amount of power required
and the excessive bruising of the potatoes. After plowing out, the
crop should be gathered promptly. In the San Joaquin Valley the
practice is to leave the potatoes attached to the central stem and gather
the crop into large piles at convenient intervals through the field.
These piles are covered with sweet potato tops to protect them from the
sun and from light frosts that are likely to occur late in the fall. As a
rule, the potatoes are sorted from the piles and packed in shipping
crates the day they are dug. This practice is probably the most con-
venient and economical where the potatoes are being dug for immediate
shipment. However, the covered piles may be left in the field for
several days. The over-sized, the cracked, the small or seed-sized, the
stringy potatoes and the stem are left on the ground to be gathered up
later. This practice makes it impossible to select healthy seed — a
thing that is best done in the field at the time of digging. When the
potatoes have been snapped from the stems, it is impossible to tell
which have come from healthy plants, and which from diseased plants.
The safest plan is to inspect the individual hills immediately after
plowing out, choosing those which show potatoes of desirable type, and
which prove to be healthy upon splitting the central stem. The smaller
sized potatoes, still attached to the stem, may then be gathered and
saved for seed purposes. A few careful growers have been successful
in selecting healthy seed from the piles, however, by inspecting the
stem of each intact hill and laying aside the " seed-size" potatoes at
the time the No. 1 potatoes are packed.
In harvesting sweet potatoes it is essential to avoid all rough
handling that tends to bruise them. The skin is very tender when the
potatoes are dug, and it is easily broken or rubbed off. Where the
flesh is exposed in this way, the molds that cause rotting are likely to
gain entrance and even if rot does not occur, a sunken discolored spot
is caused that injures the appearance. All unnecessary handling
should be avoided especially for potatoes that are to go into storage.
Storage stock should be placed in lug boxes without piling, hauled
directly to the storage house, and emptied into storage bins at once.
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA 15
For many years, the standard container for California-grown sweet
potatoes was the 100-pound crate. Experience has shown, however,
that this is too large and heavy for the best results in shipping, and
in recent years most of the crop has been packed in "Special" or
"three-quarter" crates which hold 75 to 80 pounds as packed in the
field. The inside dimensions of this crate are 9% by 14 by 22% inches.
In packing the crate is first nearly filled and then a top layer of
uniform-sized potatoes is carefully arranged so as to give a good bulge
to the cover when nailed on. The pressure from this bulge holds the
potatoes firm, thus preventing movement in the crate, and lessening the
injury to the appearance of the potatoes in a slack pack.
The U. S. Standard Grade for No. 1 sweet potatoes calls for potatoes
not less than 1% inches and not over 3% inches in diameter. These
size requirements are rather carefully observed by California growers.
The over-sized "Jumbo" potatoes as well as the cracked, cut, or other-
wise imperfect potatoes are usually not marketable, except as stock
feed. It is estimated that when barley is worth $50 a ton, sweet
potatoes are worth $15 as feed for dairy cattle. The sizes below No. 1
grade are utilized for canner stock and for seed. For canning, long
potatoes from % to 1% inches in diameter are demanded. Somewhat
smaller potatoes serve as well or better for seed. The "strings" also
have some value as feed for hogs.
Of the many varieties of sweet potatoes grown in the United States,
only a few are important in California. From the marketing stand-
point, this is fortunate, for when a district specializes on one or two
varieties of a crop it is easier to put out a standardized product and to
build up an established reputation for it. Still, the leading varieties
differ enough in their adaptability to different soils and localities,
suitability for market purposes and other characteristics, to justify the
grower in considering carefully the varietal question. Below are
discussed some of the main points connected with varieties now grown
or likely to be grown in California.
The Jersey Type. — There are several distinct strains of this general
type, which together comprise most of the commercial acreage. One
strain has been grown in this state for many years, and is generally
spoken of as the "Old California." It appears to be distinct from
any of the Eastern strains. The potatoes are long and slender, there
16 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION
are a large number to the plant, and under unfavorable growing con-
ditions many of them do not reach sufficient thickness for the market
grade. Generally, this strain produces a larger proportion of canner
and seed stock than any other variety or strain grown. Its vines are
rather slender with small leaves of variable type, some being narrow
and pointed, some distinctly forked or three-lobed, and others broadly
triangular. Another strain, grown extensively in recent years, is
generally referred to as the "New Jersey" strain, seed having been
imported from that state about 1921. This is the same as the Eastern
variety, Little Stem, or Up River. It can scarcely be distinguished
from the California strain by the appearance of the leaves or runners ;
the potatoes, however, are much shorter and thicker, more chunky or
short-spindle shaped than the California. This strain has become
very popular, as it produces a large yield with a high percentage of
No. 1 potatoes. A third strain is the Bed Jersey, quite similar to the
New Jersey strain in every respect except the intense red color of the
skin. It has no special qualities to commend it and is not in demand on
The Jersey strains in general produce well on very sandy soil, but
perhaps are the least adapted of all varieties, to the heavier soils. This
type of sweet potato has a dry mealy flesh, which is preferred by some
people. At present it is the most popular variety for summer and
fall use on the Pacific coast markets, but generally sells at a lower
price than other varieties during the winter. The various strains of
this type are rather early in maturing. The small light growth of top
and the fact that potatoes adhere to the central stem more strongly
than other varieties, are advantages in harvesting. In storage-quality,
the Jersey type is decidedly inferior to other varieties even under the
best conditions, the potatoes usually beginning to shrivel at the stem
end about a month after being placed in storage. This defect in the
Jersey type is more noticeable in California than in the East. Because
of its poor keeping quality and the market preference for other sorts
in winter, it is not advisable to store the Jersey type in commercial
quantities for more than a few weeks.
Nancy Hall. — This variety has recently been grown in California in
commercial quantities and is justly increasing in favor. The potatoes
are medium-long, spindle-shaped, tapering at both ends, smooth and
uniform when grown under favorable conditions. The skin is light
pink of uneven density. The flesh is pink while raw, becoming golden
yellow and very sweet and juicy when cooked. Many prefer this type
when they once become acquainted with it. Varieties like the Nancy
Hall having moist sweet flesh are often spoken of as "Yams" though
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA 17
the true Yam is a tropical plant belonging to another botanical family,
and is not grown in the United States. The Xancy Hall is early and
very productive. It is one of the best keeping varieties, and therefore
well suited for storage. While best adapted to the sandy soils, this
variety thrives well enough on moderately heavy soils to make a satis-
factory crop for home use. On account of the rapid early growth of
the potatoes and of their tendency to grow too large, this variety can
be dug for the extra early crop when only half grown, yet produce
satisfactory yields. Objections to this variety are : its tendency to
grow potatoes that are too large or rough ; susceptibility to Stem Rot
disease ; and difficulty in obtaining a good stand of plants in the field,
on account of small number of roots formed by the sprouts before
transplanting from the hotbed. The tendency to over-sized roots can
be corrected by setting the plants close in the row. Spacing the plants
as close as 6 inches in the row has been found to give maximum yields
on moist fertile soils.
Porto Rico. — This variety is of somewhat the same general type
as the Nancy Hall; but is considered superior in some respects. The
potatoes are of a deep coppery red and have a deep pink flesh, which is
richly colored and very sweet and juicy when cooked. The potatoes
are rather irregular, though most of them are spindle-shaped, and
of medium length. This variety has been very successfully grown in
the Los Angeles district for several years and in 1924 several small
patches grown at Turlock and Delhi proved its adaptability to the
San Joaquin Valley. Though this variety is practically unknown on
the markets of northern California and the Northwestern states, its
fine qualities will soon render it popular in these sections. It is not
particularly early, but is well suited for the main fall shipping crop
and for winter storage.
Southern Queen, — This is a large coarse-growing variety, having
white skin and cream-colored flesh. Though not in demand on the
markets, because of the white color, it is of fairly good eating quality
after it has been in storage for several months. This variety is hardly
grown at all in California. It is known in the Turlock district as
The sweet potato is commonly regarded as a difficult crop to store
over winter, because of its sensitiveness to cold and susceptibility to
rots caused by fungi when the storage conditions are defective. How-
ever, during the past ten years very satisfactory and dependable
methods for sweet potato storage have been worked out, largely by the
U. S. Department of Agriculture, and thousands of the modern storage
18 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION
houses have been erected in the southern and eastern states. California
growers have been very slow to provide suitable storage facilities for
sweet potatoes. There is only one large storage house and two small
houses of more or less modern type in the state. On account of the mild
climate, California growers have been fairly successful in storing sweet
potatoes in cellars in some years. However, conditions in these cellars
are seldom well regulated and the losses by decay and shrinkage are
generally very heavy, a total loss being a common occurrence in cold
or wet seasons. The inferior quality of cellar stock as compared to
1 ' cured, " or the storage house stock, is reflected in the much lower
prices paid for the former. Data from the San Francisco market
reports bear out this statement.
The great advantage of storing sweet potatoes is that it greatly
extends the marketing season and the period for consuming the crop.
Instead of forcing the entire crop onto the market during the digging
season, from August to November, a large part may be held in storage
for marketing during the winter and early spring. Sweet potatoes can
easily be kept as late as May 1. Thus the length of the sweet potato
season may be doubled. Unlike many vegetables, sweet potato con-
sumption is not seasonal. If available, they are used as extensively in
winter as in autumn. Development of more and better storage facili-
ties will provide an outlet for much larger crops of sweet potatoes
than have ever been grown in California.
The sweet potato requires a warm, dry, well ventilated storage place
if it is to be kept through the winter with minimum loss from shrinkage
and decay. An important factor is a preliminary "curing" or sweat-
ing process, given for the first 10 to 14 days after the potatoes go into
storage. During this period the temperature should be held at 80°
to 85° F., and the ventilators kept open so that excess moisture can
pass off from the potatoes freely. Some chemical changes occur in
the potatoes themselves during this curing process : the skins become
tougher and thicker, and the cut and bruised places seal over so that
rot-producing fungi cannot gain entrance. After curing, the storage
rooms should be held at 50° to 55° F., with the ventilators opened or
closed according to temperature and moisture conditions outdoors. The
necessary conditions for curing and holding sweet potatoes through
the winter can best be supplied in specially constructed sweet potato
houses. These houses do not have to be so substantially constructed
in California as they do in eastern states, and need not be expensive.
Persons interested in commercial storage of sweet potatoes are advised
to secure Farmers' Bulletin No. 970 from the U. S. Department of
Agriculture, Washington, D. C.
SWEET POTATO PRODUCTION IN CALIFORNIA
Fig. 6. — Showing dead plants and missing places in sweet potato field, just
before harvest. Due to black rot, chiefly.
Fig. 7. — Healthy field of sweet potatoes with practically no missing places.
Seed were carefully selected and dipped in Corrosive Sublimate solution. Nancy
Hall variety on left, Jerseys on right. A. R. Vierra, Turlock, California.
20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
The sweet potato is subject to several destructive diseases, affecting
both the plant and the potato, and to some diseases which attack the
potato only. These diseases have been increasing in severity in recent
years. Some of them are prevalent at the present time, and are the
cause of great loss to the growers who often are not aware of them.
The control of disease is the chief problem now confronting California
growers, from the standpoint of production.
During the summer of 1923 and 1924 many fields in the main
sweet potato districts were visited by the writer. In most cases some
disease was present, and in some fields 40 to 50 per cent of the plants
were dead or dying of disease. There can be little profit with such a
large reduction in the stand. It costs as much to plant, cultivate, and
irrigate a field with only half a stand of plants as with a full stand.
Losses of plants of only 10 or 15 per cent, which may not even be
noticed by the grower, will reduce the yield in nearly the same ratio,
which in years of low prices may entirely prevent all profit. Losses
of plants just after transplanting are often attributed by growers to
causes other than disease, while death of plants during the growing
season often passes unnoticed. The chief diseases are so widely spread
and may cause such heavy losses that the simple specific measures for
preventing them should always be followed, whether or not the growers
know them to be present.
The two diseases which cause most loss in California, commonly
known as stem rot and black rot, are prevalent in other parts of the
country also, and their control has been carefully worked out. For-
tunately, investigations carried out in 1923 and 1924 by Dr. J. L.
Weimar of the U. S. Department of Agriculture, in cooperation with
the Farm Advisors of Stanislaus, Merced, Los Angeles, and Orange
counties, demonstrated that the same control measures that have proved
so effective in the eastern states will also control these diseases in
California. The chief diseases are briefly described below and on the
last page is given a summary of the methods of control.
Black Rot. — This disease is caused by a fungus which attacks the
underground part of the stem as well as the potatoes. Decayed spots
of varying size appear upon the potatoes. These spots are black on
the surface and somewhat sunken. The decay often starts in growth
cracks or in places wounded by gophers; while in storage, cuts and
bruises are the chief starting points. The decay is not very deep and
if cut away the sound flesh below turns a greenish color soon after
ClRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA
Fig. 8. — Selecting seed from cull-pile in the field. The wrong way to
get healthy seed.
-The right way to select seed sweet potatoes. The hills are laid
out and stem of each one is examined for disease.
22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
exposure to air. The flesh just below the decayed spots is very bitter
and when potatoes affected with black rot are cooked the bitterness
permeates the whole potato. This disease is often found on seed stock
in the spring as black patches on the sides, or as a dry, shriveled and
blackened condition at the stem end of the potato. On the plant, infec-
tion by Black Rot may be first noted at the time the plants are pulled
in the hotbed for transplanting. At this stage the stem is black and
decayed for a short distance from its basal end. Such plants die soon
if transplanted to the field, although sometimes when conditions are not
favorable for the development of the disease, they may grow and
produce several potatoes which are likely to be diseased. Many plants
Fig. 10. — Black rot on sweet potato, showing surface decay. (U.S.D.A.)
that do not show infection when pulled for transplanting may really
be infected and die after transplanting. Infected plants which do not
die in the early part of the season, may be recognized at harvest time
by the dry black decay of the lower part of the central stem. Such
plants usually produce only a few small potatoes.
The black rot fungus attacks no plant but sweet potatoes, yet it
may survive in the soil over winter and even for several years. Rota-
tion of crops is therefore a necessity as a part of any method of control.
But if the soil is free from disease to begin with and all the other
measures to prevent infection are observed, several crops of sweet
potatoes may be grown in succession on the same land. The most
important cause of infection is the use of infected seed. If potatoes
showing black rot are bedded in the plant .bed, the fungus grows
from the mother potato and attacks the new plants. Even seed
potatoes that appear to be healthy, generally have a plentiful supply
of the fungus on their surface, if they have been stored in bins with
SWEET POTATO PRODUCTION IN CALIFORNIA
infected potatoes. However, healthy plants may be grown from seed
of this kind if it is disinfected before bedding according to the direc-
tions given on page 8, and bedded in a disease-free hotbed. The seed
potatoes that have visible signs of Black Rot should be sorted out at
bedding time and destroyed as they cannot be disinfected.
Another source of infection is the soil of the plant bed. On many
farms there is only one spot that is sunny, sheltered from wind and
accessible to water. The tendency is to make the sweet potato plant
bed in this one favored spot year after year. When plant pulling is
Fig. 11. — Black rot on sweet potato plants, upon removal from hotbed.
finished in the spring, the old beds are left without further attention
until bedding time the next spring. By this time the soil in and around
the beds is likely to be saturated with the fungous organisms that
cause black rot and other diseases, which have spread from the decay-
ing seed potatoes of the previous year. In fact, many growers prefer
to make their plant beds on the same spot as in previous years because
of the improvement in physical texture of the soil through the incor-
poration of the decayed seed, plants and manure of previous years.
The result is a plant bed soil thoroughly infected with diseases which
infects each new crop of plants in turn. There are three remedies for
this situation. One is to make the plant beds in a fresh spot each
year — but this is not always possible. Another is to sterilize the soil
24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
before preparing the plant bed each spring. Drenching the soil with a
solution of formaldehyde (one pint to 30 gallons of water) at the rate
of one gallon to each square foot of surface would probably disinfect
old hotbed soils so that they could be used again. Generally, however,
the most /practical method is to make the plant bed with fresh soil or
sand hauled from a place where contamination by sweet potato disease
is not likely, such as a dry creek bed. With a layer of this soil or
sand 3 or 4 inches deep below the seed potatoes, and a covering of the
same material, the chances of infection reaching the plants from with-
out are slight.
Stem Rot. — This disease, like black rot, is caused by a fungus that
may live in the soil for several years. It attacks both the potatoes and
the stems, but differs from black rot in that it develops entirely within
the tissues, being seldom visible from the exterior until the plant dies.
Potatoes borne by diseased plants usually contain the disease, and as
they are likely to be small and therefore used for seed purposes, they
are one of the chief causes of the spread of the disease from year to
year. In advanced stages, potatoes affected with stem rot show a
blackened ring just below the skin, but so many in less advanced
stages do not show this ring that healthy seed cannot be secured by
discarding those that do not show this discoloration. The only way to
secure absolutely healthy seed is to select them from healthy plants at
digging time. Each hill should be inspected by splitting the central
stem. If the interior is brownish in color, the plant is infected with
stem rot, and the potatoes it bears are not suitable for seed. This
disease also occurs on the young plants in the hotbed, the leaves becom-
ing yellowish and the underground part of the stem bluish in color.
These plants generally die before or soon after transplanting. One
of the commonest causes of poor stands in the fields is the early death
of a large number of plants that became diseased in the hotbed. When
the soil of the field contains this disease more plants become infected
during the growing season. Such plants are distinguished by their
yellowish or brown leaves, and by the blackened dead vines. They often
have formed several potatoes, and after the disease kills the central
stem these potatoes send up sprouts similar to those ordinarily pro-
duced in the hotbed. The typical appearance of plants thus affected is
shown in fig. 13. Other plants affected still later may show no sign
of disease until the stems are split during seed inspection at digging
Cmc. 285] SWEET POTATO PRODUCTION IN CALIFORNIA
Fig. 12. — Stem rot of sweet potato, showing the discoloration of
vascular tissue. (U.S.D.A.)
Fig. 13. — Stem rot often affects plants as shown in the center — the vines
have died and sprouts have grown out from the little potatoes already formed.
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
Fig. 14. — Soft rot, showing the luxuriant growth of the fungus on the
surface, which often occurs in storage. (U.S.D.A.)
SWEET POTATO PRODUCTION IN CALIFORNIA
Scurf. — This disease is caused by a fungus that occurs in many
soils, even where sweet potatoes have never been grown. It is most
likely to affect potatoes on soils which are heavy or very moist. It
causes small black spots on the skin which in severe cases run together,
giving the potatoes a splotched or stained appearance. These diseased
areas are superficial, seldom extending deeper than the skin, and doing
no damage aside from producing their unsightly appearance. The
disease is prevented to a large extent by the same methods as those
given for black rot.
Fig. 15. — King rot of sweet potato — caused by same fungus as soft rot.
Soft Rot. — This disease occurs to a small extent in the field, but
does its main damage during storage. It is caused by one of the most
common molds, spores of which are in the soil and floating in the air
everywhere. Fortunately, this mold is unable to penetrate the normal
healthy skin, being able to enter the potato only through cuts and
bruises. Hence, careful handling of storage stock lessens the chances
of decay. Curing the sweet potatoes in warm dry houses just after
digging increases their resistance to this decay, while cold, damp
storage, as well as handling or sorting while in storage, greatly
increases the chances of its occurrence. The same organism often
produces a dry brownish decay known as ring rot. This usually
28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
affects only portions of the tuber while soft rot renders the whole
Nematodes. — Nematode injury, usually called root knot, occurs on
sweet potatoes to some extent, but the injury to this crop is not so
severe as it is to tomatoes, melons, and other garden vegetables. In
fact, very satisfactory crops of sweet potatoes can be grown on soils
so thoroughly infested with nematodes that it is impossible to grow
most of the common vegetables and fruits. Nematode injury appears
as small galls on the fibrous roots of the sweet potato plant, and as
larger galls on the root end of the potatoes. Nematodes are easily
spread from place to place by sweet potato plants; therefore, unless
one is absolutely sure that the plants are free of nematodes, sweet
potatoes should not be grown in young orchards on sandy land where
nematode infestation would have serious and permanent results.
Nematodes are most serious on light sandy soils. It is said that they
can be starved out by growing crops immune to nematodes for two
years. All cereal crops and the Iron. and Brabham varieties of cow
peas are immune.
THE DISEASE CONTEOL PEOGEAMME
The grower of sweet potatoes when once he realizes the losses caused
by the common diseases, will wish to control not only one, but all of
them, especially as he may not know which one of the diseases is doing
the damage. Fortunately, the control of each of the common diseases
requires practically the same treatments. No one treatment will be
effective against any disease, hence, it is necessary to follow a pro-
gramme of several distinct steps.
1. In the fall, healthy seed should be selected from healthy plants.
The stems of the plants are split at digging time, and seed saved only
from plants that show no internal discoloration. This selected seed
should be kept separate from other potatoes in storage to avoid the
possibility of infection. It should be stored in new boxes, or in old
boxes that have been disinfected with bluestone solution (1 pound to
25 gallons of water).
2. Just before bedding time in the spring, the seed stock should
be sorted over. All potatoes showing black rot or other decay must
3. Make the hotbed in a new place each year or use fresh soil or
sand in preparing it.
CIRC. 285] SWEET POTATO PRODUCTION IN CALIFORNIA 29
4. Do not let decayed potatoes become mixed with the soil or the
manure used in making the hotbed, and do not leave them lying about
near the bed.
5. Disinfect the seed before bedding, by dipping it for 10 minutes
in a solution of corrosive sublimate ( 4 ounces to 32 gallons of water).
See page 8 for details.
6. Discard all plants that show any evidence of disease when pull-
ing for transplanting, especially those showing black or bluish dis-
coloration on the basal portion of the stem.
7. Grow sweet potatoes wherever possible on land that has not been
used for this crop in several years.
8. Try to grow healthy seed and healthy plants at home rather
than buy them from some other section where diseases are likely to
be just as common.
STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION
253. Irrigation and Soil Conditions in the 352.
Sierra Nevada Foothills, California.
261. Melaxuma of the Walnut, "Juglans 353.
262. Citrus Diseases of Florida and Cuba 357.
Compared with Those of California.
263. Size Grades for Ripe Olives.
268. Growing and Grafting Olive Seedlings. 358.
273. Preliminary Report on Kearney Vine-
yard Experimental Drain. 359.
275. The Cultivation of Belladonna in Cali- 361.
276. The Pomegranate. 362.
277. Sudan Grass 363.
278. Grain Sorghums.
279. Irrigation of Rice in California. 364.
280. Irrigation of Alfalfa in the Sacramento
283. The Olive Insects of California.
285. The Milk Goat in California. 367.
286. Commercial Fertilizers.
294. Bean Culture in California. 368.
304. A Study of the Effects of Freezes on
Citrus in California. 369.
310. Plum Pollination. 370.
312. Mariout Barley. 371.
313. Pruning Young Deciduous Fruit Trees.
319. Caprifigs and Caprification. 372.
324. Storage of Perishable Fruit at Freezing
325. Rice Irrigation Measurements and Ex-
periments in Sacramento Valley,
328. Prune Growing in California.
331. Phylloxera-Resistant Stocks. 376.
334. Preliminary Volume Tables for Second-
Growth Redwood. 377.
335. Cocoanut Meal as a Feed for Dairy 379.
Cows and Other Livestock. 380.
339. The Relative Cost of Making Logs from
Small and Large Timber. 381.
340. Control of the Pocket Gopher in Cali-
343. Cheese Pests and Their Control.
344. Cold Storage as an Aid to the Market- 383.
ing of Plums.
346. Almond Pollination. 384.
347. The Control of Red Spiders in Decidu-
348. Pruning Young Olive Trees. 385.
349. A Study of Sidedraft and Tractor 386.
350. Agriculture in Cut-over Redwood Lands. 387.
Further Experiments in Plum Pollina-
Bovine Infectious Abortion.
Results of Rice Experiments in 1922.
A Self-mixing Dusting Machine for
Applying Dry Insecticides and
Black Measles, Water Berries, and
Related Vine Troubles.
Fruit Beverage Investigations.
Preliminary Yield Tables for Second
Dust and the Tractor Engine.
The Pruning of Citrus Trees in Cali-
Fungicidal Dusts for the Control of
Turkish Tobacco Culture, Curing and
Methods of Harvesting and Irrigation
in Relation to Mouldy Walnuts.
Bacterial Decomposition of Olives dur-
Comparison of Woods for Butter Boxes.
Browning of Yellow Newtown Apples.
The Relative Cost of Yarding Small
and Large Timber.
The Cost of Producing Market Milk and
Butterfat on 246 California Dairies.
A Survey of Orchard Practices in the
Citrus Industry of Southern Cali-
Results of Rice Experiments at Cor-
Sun-Drying and Dehydration of Wal-
The Cold Storage of Pears.
Walnut Culture in California.
Growth of Eucalyptus in California
Growing and Handling Asparagus
Pumping for Drainage in the San
Joaquin Valley, California.
Monilia Blossom Blight (Brown Rot)
A Study of the Relative Values of Cer-
tain Succulent Feeds and Alfalfa Meal
as Sourses of Vitamin A for Poultry.
Pollination of the Sweet Cherry.
Pruning Bearing Deciduous Fruit
Correspondence Courses in Agriculture.
The Selection and Cost of a Small
The Control of Citrus Insects.
136. Melilotus indica as a Green-Manure
Crop for California.
Oidium or Powdery Mildew of the Vine.
Feeding and Management of Hogs.
Some Observations on the Bulk Hand-
ling of Grain in California.
Irrigation Practice in Growing Small
Fruit in California.
155. Bovine Tuberculosis.
157. Control of the Pear Scab.
160. Lettuce Growing in California.
161. Potatoes in California.
164. Small Fruit Culture in California.
165. Fundamentals of Sugar Beet Culture
under California Conditions.
166. The County Farm Bureau.
167. Feeding Stuffs of Minor Importance.
170. Fertilizing California Soils for the 1918
173. The Construction of the Wood-Hoop
178. The Packing of Apples in California.
CIRCULARS — (Continued)
179. Factors of Importance in Producing
Milk of Low Bacterial Count.
184. A Flock of Sheep on the Farm.
190. Agriculture Clubs in California.
199. Onion Growing in California.
202. County Organizations for Rural Fire
203. Peat as a Manure Substitute.
208. Summary of the Annual Reports of the
Farm Advisors of California.
209. The Function of the Farm Bureau. _
210. Suggestions 'to the Settler in California.
212. Salvaging Rain-Damaged Prunes.
214. Seed Treatment for the Prevention of
215. Feeding Dairy Cows in California.
217. Methods for Marketing Vegetables in
220. Unfermented Fruit Juices.
228. Vineyard Irrigation in Arid Climates.
231. The Home Vineyard.
232. Harvesting and Handling California
Cherries for Eastern Shipment.
233. Artificial Incubation.
234. Winter Injury to Young Walnut Trees
235. Soil Analysis and Soil and Plant Inter-
236. The Common Hawks and Owls of Cali-
fornia from the Standpoint of the
237. Directions for the Tanning and Dress-
238. The Apricot in California.
239. Harvesting and Handling Apricots and
Plums for Eastern Shipment.
240. Harvesting and Handling Pears for
241. Harvesting and Handling Peaches for
243. Marmalade Juice and Jelly Juice from
244. Central Wire Bracing for Fruit Trees.
245. Vine Pruning Systems.
247. Colonization and Rural Development.
248. Some Common Errors in Vine Pruning
and Their Remedies.
249. Replacing Missing Vines.
250. Measurement of Irrigation Water on
251. Recommendations Concerning the Com-
mon Diseases and Parasites of
Poultry in California.
252. Supports for Vines.
253. Vineyard Plans.
254. The Use of Artificial Light to Increase
Winter Egg Production.
255. Leguminous Plants as Organic Fertil-
izer in California Agriculture.
256. The Control of Wild Morning Glory.
257. The Small-Seeded Horse Bean.
258. Thinning Deciduous Fruits.
259. Pear By-products.
260. A Selected List of References Relating
to Irrigation in California.
261. Sewing Grain Sacks.
262. Cabbage Growing in California.
263. Tomato Production in California.
264. Preliminary Essentials to Bovine Tuber-
265. Plant Disease and Pest Control.
266. Analyzing the Citrus Orchard by Means
of Simple Tree Records.
267. The Tendency of Tractors to Rise in
Front; Causes and Remedies.
268. Inexpensive Lavor-saving Poultry Ap-
269. An Orchard Brush Burner.
270. A Farm Septic Tank.
271. Brooding Chicks Artificially.
272. California Farm Tenancy and Methods
273. Saving the Gophered Citrus Tree.
275. Marketable California Decorative
276. Home Canning.
277. Head, Cane, and Cordon Pruning of
278. Olive Pickling in Mediterranean Coun-
279. The Preparation and Refining of Olive
Oil in Southern Europe.
281. The Results of a Survey to Determine
the Cost of Producing Beef in Cali-
282. Prevention of Insect Attack on Stored
283. Fertilizing Citrus Trees in California.
284. The Almond in California.
The publications listed above may be had by addressing
College of Agriculture,
University of California,